The burst storm came from SGR J1550−5418, a neutron star with a super-strong magnetic field, also known as a magnetar. Located about 15,000 light-years away in the constellation Norma, the magnetar was quiet until October 2008, when it entered a period of eruptive activity that ended in April 2009.

At times, the object produced hundreds of bursts in as little as 20 minutes, and the most intense explosions emitted more total energy than the sun does in 20 years. High-energy instruments on many spacecraft, including NASA's Swift and Rossi X-ray Timing Explorer, detected hundreds of gamma-ray and X-ray blasts.

An examination of 263 individual bursts detected by Fermi's Gamma-ray Burst Monitor confirms vibrations in the frequency ranges previously only seen in rare giant flares from magnetars. Astronomers suspect these are twisting oscillations of the star where the crust and the core, bound by the magnetic field, vibrate together. In addition, a single burst showed an oscillation at a frequency never seen before and which scientists still do not understand.

While there are many efforts to describe the interiors of neutron stars, scientists lack enough observational detail to choose between differing models. Neutron stars reach densities far beyond the reach of laboratories and their interiors may exceed the density of an atomic nucleus by as much as 10 times. Knowing more about how bursts shake up these stars will give theorists an important new window into understanding their internal structure.Magnetar Burst with Torsional Waves

A rupture in the crust of a highly magnetized neutron star, shown here in an artist's rendering, can trigger high-energy eruptions. Fermi observations of these blasts include information on how the star's surface twists and vibrates, providing new insights into what lies beneath. The subtle pattern on the surface represents a twisting motion imparted to the magnetar by the explosion.

A rupture in the crust of a highly magnetized neutron star, shown here in an artist's rendering, can trigger high-energy eruptions. Fermi observations of these blasts include information on how the star's surface twists and vibrates, providing new insights into what lies beneath.

This image, taken in May 2008 as the Fermi Gamma-ray Space Telescope was being readied for launch, highlights the detectors of the spacecraft's Gamma-ray Burst Monitor (GBM). The GBM is an array of 14 crystal detectors designed for transient lower-energy gamma-ray outbursts, such as TGFs. Labeled.